Processes or threads doing I/O during transparent CFS failover get stuck waiting in I/O. They cannot be interrupted. If they are part of a thread group zombies can also appear.
How to reproduce: Start reading a large file on a CFS hard mount on the surviving OpenSSI node and force CFS to transparently failover. The application on the surviving OpenSSI node is expected to continue uninterrupted and finish reading the entire file, but instead gets stuck waiting in I/O.